Silicone compounds whose main components are an alkenyl group-containing organosiloxane and an organohydrogenpolysiloxane and which cure in the presence of a platinum-based catalyst are called addition reaction-curing silicone compositions, and are used in many different fields of industry. However, when this type of silicone composition cures, the surface thereof becomes inert, which makes it extremely difficult to bond an epoxy resin, phenol resin, or any of various other organic resins to this cured material. Various attempts have therefore been made at bonding these materials together, such as subjecting the surface of a cured product of an addition reaction-curing silicone composition to an ozone treatment, then bringing one of various organic resins into contact with this ozone-treated surface and curing it. This method, however, is not satisfactory for practical purposes because of its drawback in that adhesion decreases over time. Accordingly, there is a need for an adhesion imparter for bonding various organic resins to the cured product of an addition reaction-curing silicone composition. It is believed that an organosilicon compound containing hydroxyphenyl groups (as functional groups for enhancing adhesion with an organic resin) and alkenyl groups (as functional groups incorporated into the addition reaction cured product) in the same molecules would be effective as this adhesion imparter.